Optical disc controller and optical disc device having the same

ABSTRACT

An optical disc controller for an optical disc drive playing optically a first information storage medium and a second information storage medium having a higher storage density than the first medium. The controller includes: a rotation control section for controlling a rotating mechanism rotating the media; an equalizer for removing first frequency range components from an RF playback signal, obtained by irradiating each media with light and detecting reflected light, and amplifying second frequency range components; and a phase locking section for generating a sync clock signal to do synchronization detection with a digital playback signal obtained by digitizing the output of the equalizer. The rotation control section rotates the media while controlling the rotating mechanism such that RF playback signals are obtained at first and second transfer rates. The maximum playback frequency of the RF playback signal obtained from the first medium at the first transfer rate is substantially equal to that of the RF playback signal obtained from the second medium at the second transfer rate.

TECHNICAL FIELD

The present invention relates to an optical disc drive that can processeither two or more types of information storage media or at least twodifferent transfer rate modes. More particularly, the present inventionrelates to an optical disc controller for controlling a read clocksignal for an information storage medium and its number of revolutionsand also relates to an optical disc drive including such an optical disccontroller.

BACKGROUND ART

A CD (compact disc) was originally developed as an information storagemedium (which will be referred to herein as a “disc”) to record musicthereon. Nowadays, however, the CD is also extensively used as aninformation storage medium for computers. Meanwhile, DVDs (digitalversatile discs) and other types of discs, which are developed ashigh-density multi-purpose media from the outset, are also on the marketnow. Under the circumstances such as these, there is an increasingdemand for a system that can play multiple types of discs with mutuallydifferent storage densities (such as CDs and DVDs) by itself.Furthermore, a system that can write data on multiple types of discswith mutually different storage densities has been put on the marketrecently.

In such a system that can read or write information from/on multipletypes of discs, the user picks a type of disc according to the type ofinformation to be read and/or written. For example, as for musicinformation or PC (personal computer) data with a relatively smallcapacity, a CD-ROM disc, a recordable CD-R disc, or a rewritable CD-RWdisc is normally used. On the other hand, as for video information or PCdata with a relatively big capacity, a DVD-ROM disc or a rewritableDVD-RAM disc or DVD-RW disc is used. Furthermore, to store high-qualityvideo of a BS digital broadcast, a huge capacity (e.g., 20 GB or more)storage medium, which uses a blue laser beam, has recently beendeveloped as a highly prospective product.

Among various optical disc drives for PCs, optical disc drives thatadopt a constant angular velocity (CAV) writing technique, characterizedby using different transfer rates for inside and outside portions of thesame medium, recently outnumber optical disc drives that adopt aconstant linear velocity (CLV) writing technique, characterized by usingthe same transfer rate at any read location on the disc, in order toincrease the highest transfer rate and access performance in CD-ROMs orDVD-ROMs, for example. Such a drive usually performs a playbackoperation at as high a transfer rate as possible, which is defined bythe highest possible performance of the drive, but sometimes cannotperform a playback operation at all due to a scratch or dirt on theinformation storage side of the disc or the degree of eccentricity orshifted center of mass. To avoid such a situation, the function ofchanging the rotational velocities and switching the transfer ratesaccording to the disc state has recently been introduced.

Hereinafter, the procedure of retrieving information from an opticaldisc will be described briefly. First, a laser beam is radiated towardthe information storage side of the optical disc and its reflected lightis detected at an optical pickup and then amplified by an RF amplifier,thereby generating an RF playback signal representing the quantity oflight reflected. The RF playback signal generated in this manner thenhas its RF noise (which is located outside of its signal frequency band)removed by an equalizer. Also, in the vicinity of its high frequencycomponents that have had their amplitudes decreased due to intersymbolinterference, the RF playback signal is boosted. Thereafter, the RFplayback signal is digitized to generate read data. Meanwhile, a readclock signal, which is in phase with the read data, is generated fromthe read data by a PLL (phase-locked loop) circuit. Subsequently, ademodulating section generates decoded information from the read dataand read clock signal, and then the information is transferred to a hostby way of an interface circuit (such as ATAPI or SCSI).

In this procedure, if the types of discs to play or the play modesthereof are different, then the data transfer rates and the RF frequencybands of the read data are also different. More specifically, thefrequency band to be extracted and boosted by the equalizer and thefrequency of the clock signal to be generated by the PLL circuit changewith the type of the disc to play and the play mode thereof. The readclock signal is determined by the transfer rate and the reference clockfrequency as defined by the disc standard (e.g., about 27 MHz for aDVD-ROM). Accordingly, if discs to play or transfer rate modes thereofare changed, then multiple lines of those frequency-dependent circuitsare prepared for an optical disc drive and switched depending onspecific conditions.

If the read and write operations are carried out by the CLV technique,then the transfer rate is constant and just one line of equalizer andPLL is required. On the other hand, if the read and write operations arecarried out by the CAV technique, then the transfer rate changes with aread radial location on the disc. Accordingly, those frequency-dependentcircuits need to change their processing reference frequencies accordingto the read radial location, too.

For these reasons, a conventional CAV optical disc drive that canprocess multiple types of discs chooses one of a plurality ofdemodulating sections corresponding to those types of discs during itsloading, for example. Then, the optical disc drive divides the disc readlocations into a number of radial zones. In reading data from therespective zones, the selected demodulating section sequentially picksone of multiple circuits, associated with the respective transfer rates,after another.

Hereinafter, a conventional optical disc drive that can process multipletypes of discs in multiple play modes will be described with referenceto the accompanying drawings.

FIG. 24 is a block diagram showing a conventional optical disc. In thefollowing example, a drive that uses a CD and a DVD as two types ofdiscs and can play the DVD in two different playback modes (i.e.,high-speed and low-speed modes) will be described. In FIG. 24, threelines of equalizer sections 2003, 2004 and 2005 and PLL sections 2006,2007 and 2008 are provided. Also, a CD demodulating section 2009 and aDVD demodulating section 2010 are provided as two demodulating sections.These circuits are selectively used by a disc type selector 2001 and aplayback mode selector 2002.

In playing a CD, an infrared laser diode 1021 with a wavelength of 780nm is activated and a predetermined CD light beam 1023 is produced byoptical members (not shown) in the optical pickup. On the other hand, inplaying a DVD, a red laser diode 1022 with a wavelength of 650 nm isactivated and a predetermined DVD light beam (not shown) is produced byoptical members (not shown) in the optical pickup.

When these two laser diodes or light beams are switched, the disc typeselector 2001 selects the circuits required. For example, in playing aCD, the disc type selector 2001 connects contacts A and C together.Then, an RF playback signal, which has been detected by the opticalpickup 103 from the optical disc 102 being rotated by a disc motor 101,is amplified by an RF amplifier 104. The amplified RF playback signalpasses the disc type selector 2001 and is input to the equalizer section2003. The equalizer section 2003 boosts the RF playback signal in asignal frequency band that is suited to playing the CD, therebygenerating an RFEQ signal.

Then, a digitizing section 106 digitizes the RFEQ signal, therebygenerating read data. From this read data, the PLL section 2006generates a read clock signal. Using this read data and read clocksignal, the CD demodulating section 2009 demodulates the informationthat is stored on the CD and then transfers the information to a host(not shown).

For example, in playing a DVD at the higher speed, the disc typeselector 2001 connects contacts C and B together and the play modeselector 2002 connects contacts D and F together. Then, an RF playbacksignal, which has been detected by the optical pickup 103 from theoptical disc 102 being rotated by the disc motor 101, is amplified bythe RF amplifier 104. The amplified RF playback signal passes the disctype selector 2001 and mode selector 2002 and is input to the equalizersection 2005. The equalizer section 2005 boosts the RF playback signalin a signal frequency band that is suited to playing the DVD at thehigher speed, thereby generating an RFEQ signal.

Then, the digitizing section 106 digitizes the RFEQ signal, therebygenerating read data. From this read data, the PLL section 2008generates a read clock signal. Using this read data and read clocksignal, the CD demodulating section 2010 demodulates the informationthat is stored on the DVD and then transfers the information to the host(not shown).

For example, in playing a DVD at the lower speed, the disc type selector2001 connects contacts C and B together and the play mode selector 2002connects contacts D and E together. Then, an RF playback signal, whichhas been detected by the optical pickup 103 from the optical disc 102being rotated by the disc motor 101, is amplified by the RF amplifier104. The amplified RF playback signal passes the disc type selector 2001and mode selector 2002 and is input to the equalizer section 2004. Theequalizer section 2004 boosts the RF playback signal in a signalfrequency band that is suited to playing the DVD at the lower speed,thereby generating an RFEQ signal.

Then, the digitizing section 106 digitizes the RFEQ signal, therebygenerating read data. From this read data, the PLL section 2007generates a read clock signal. Using this read data and read clocksignal, the CD demodulating section 2010 demodulates the informationthat is stored on the DVD and then transfers the information to the host(not shown).

As described above, the conventional optical disc drive that can copewith multiple types of discs and multiple transfer rate modes performsread and write operations on those discs by using at least two lines ofequalizer sections, PLL sections and demodulating sections. Accordingly,as the number of disc types or transfer rate modes to be handledincreases, the circuit scale increases correspondingly.

Thus, to reduce the circuit scale, a configuration, in which a registercircuit is provided for these circuits and variables depending on thedisc types and transfer modes are changed by modifying the parameters tobe set for the register, may be used.

In that case, however, the parameters setting the operating frequenciesof a servo circuit (or servo block) or a PLL section (or PLL block)should be defined for each disc type (e.g., CD or DVD), each transferrate mode (e.g., 16×, 8×, 4× or 2×) and each disc radial location fromwhich information is retrieved. For that purpose, a setting table areais usually provided in the program area of a system controller so as tostore all of those parameters associated with the respective disc types,transfer rate modes and radial locations. In the drive described above,supposing the register to be set has 64 bytes, the setting table area inthe program area needs 192 bytes to play a CD and a DVD that isprocessible at two transfer rates.

In that case, every time the number of types of discs to play and thenumber of transfer rate modes to be supported increase, the requiredmemory capacity increases significantly, thus raising the cost of theoptical disc drive, which is a serious problem to solve.

DISCLOSURE OF INVENTION

In order to overcome the problems described above, an object of thepresent invention is to provide an optical disc controller and anoptical disc drive, which can cope with a number of different types ofdiscs and a plurality of transfer rate modes and yet have a simpleconfiguration.

An optical disc controller according to the present invention is used inan optical disc drive that plays optically a first information storagemedium and a second information storage medium having a higher storagedensity than that of the first information storage medium. The opticaldisc controller includes: a rotation control section for controlling arotating mechanism that rotates the first and second information storagemedia; an equalizer for removing first frequency range components froman RF playback signal, obtained by irradiating each of the first andsecond information storage media with light and detecting lightreflected therefrom, and for amplifying the amplitude of secondfrequency range components thereof; and a phase locking section forgenerating a sync clock signal to do synchronization detection withrespect to a digital playback signal that is obtained by digitizing theoutput of the equalizer. The rotation control section rotates the firstand second information storage media while controlling the rotatingmechanism such that RF playback signals are obtained at a first transferrate and at a second transfer rate, respectively. The maximum playbackfrequency of the RF playback signal obtained from the first informationstorage medium at the first transfer rate is substantially equal to thatof the RF playback signal obtained from the second information storagemedium at the second transfer rate.

In one preferred embodiment, supposing channel clock frequencies of thefirst and second information storage media are A and B, respectively,the second transfer rate is n (where 1≦n) times as high as a standardtransfer rate of the second information storage medium and the firsttransfer rate is n×(B/A) times as high as a standard transfer rate ofthe first information storage medium.

In another preferred embodiment, the rotation control section controlsthe rotating mechanism such that the first and second informationstorage media rotate at a constant linear velocity.

In another preferred embodiment, the rotation control section controlsthe rotating mechanism such that the first and second informationstorage media rotate at a constant angular velocity.

In another preferred embodiment, the equalizer is operated by beingprovided with a pair of setting constants that defines the first andsecond frequency ranges, respectively. The same pair of settingconstants is applied to the first and second frequency ranges either atthe first transfer rate or at the second transfer rate.

In another preferred embodiment, the phase locking section includes avoltage controlled oscillator and a frequency divider, which areoperated at respective predetermined frequencies by being provided withtheir setting constants. The same pair of setting constants is providedfor the voltage controlled oscillator and the frequency divider eitherat the first transfer rate or at the second transfer rate.

In another preferred embodiment, the phase locking section includes afrequency divider for dividing the frequency by an integer.

In another preferred embodiment, the optical disc drive also performs awrite operation on the first and second information storage media. Theoptical disc controller further includes a movement control section fordriving a moving mechanism that moves an optical pickup in a radialdirection of the first or second information storage medium. The opticalpickup is used to read or write a signal from/on the first and secondinformation storage media. The movement control section and the rotationcontrol section control the moving mechanism and the rotating mechanism,respectively, such that after a read or write operation has beenperformed on the first or second information storage medium for apredetermined period of time at a constant linear velocity for a firstlocation in the radial direction while the first or second informationstorage medium is being rotated at a first rotation velocity so as toachieve a transfer rate that is higher than a standard read or writerate for the first or second information storage medium, a write or readoperation is performed on the first or second information storage mediumat the first rotation velocity and at a constant angular velocity for asecond location.

Another optical disc controller according to the present invention isused in an optical disc drive that plays optically an informationstorage medium in at least two different transfer rates. The opticaldisc controller includes: a rotation control section for controlling arotating mechanism that rotates the information storage medium; adigitizing section for digitizing an RF playback signal obtained fromthe information storage medium, thereby outputting read data; and aphase locking section, which includes a plurality of frequency dividerswith integral frequency division ratios and generates a sync clocksignal that is in phase with the read data. The phase locking sectiongenerates the sync clock signal by switching the frequency dividersaccording to the type of the information storage medium or the transferrate. And the rotation control section controls the rotating mechanismsuch that the information storage medium has a rotation velocitycorresponding to the frequency division ratio.

In one preferred embodiment, the second location is closer to the outeredge of the information storage medium than the first location is.

In another preferred embodiment, the second location is closer to theinner edge of the information storage medium than the first location is,and the transfer rate at the first location is at least 2.4 times ashigh as the standard transfer rate.

Still another optical disc controller according to the present inventionis used in an optical disc drive that plays optically an informationstorage medium. The optical disc controller includes: a digitizingsection for digitizing an RF playback signal obtained from theinformation storage medium, thereby outputting read data; and a phaselocking section, which includes a phase difference detector, a low passfilter, a voltage controlled oscillator and a frequency divider andgenerates a sync clock signal that is synchronized with the read data.The ratio of a lower limit frequency of a channel clock pulse, generatedby the voltage controlled oscillator, to an upper limit frequencythereof is equal to a radius ratio of the innermost edge of theinformation storage medium to the outermost edge thereof.

Yet another optical disc controller according to the present inventioncontrols an optical disc drive that performs read and write operationson an information storage medium. The optical disc controller includes:a movement control section for driving a moving mechanism that moves anoptical pickup in a radial direction of the information storage mediumto read or write information from/on the information storage medium; anda rotation control section for controlling a rotating mechanism thatrotates the information storage medium. The movement control section andthe rotation control section control the moving mechanism and therotating mechanism, respectively, such that after a read or writeoperation has been performed on the information storage medium for apredetermined period of time at a constant linear velocity for a firstlocation in the radial direction while the information storage medium isbeing rotated at a first rotation velocity so as to achieve a transferrate that is higher than a standard read or write rate for theinformation storage medium, a write or read operation is performed onthe information storage medium at the first rotation velocity and at aconstant angular velocity for a second location that is closer to theouter edge than the first location is.

An optical disc drive according to the present invention includes: anoptical pickup for obtaining RF playback signals by irradiating a firstinformation storage medium and a second information storage medium,having a higher storage density than that of the first informationstorage medium, with light and detecting light reflected therefrom; arotating mechanism for rotating the first and second information storagemedia; and any of the optical disc controllers described above.

Another optical disc drive according to the present invention includes:an optical pickup for writing a signal on a first information storagemedium and a second information storage medium, having a higher storagedensity than that of the first information storage medium, byirradiating the first and second information storage media with lightand for obtaining RF playback signals by irradiating the first andsecond information storage media with light and detecting lightreflected therefrom; a rotating mechanism for rotating the first andsecond information storage media; a moving mechanism for moving theoptical pickup in a radial direction of the first and second informationstorage media; and the optical disc controller that can perform a writeoperation as described above.

An optical disc drive controlling method according to the presentinvention is a method for controlling an optical disc drive that playsoptically a first information storage medium and a second informationstorage medium having a higher storage density than that of the firstinformation storage medium. The method includes the steps of: rotatingthe first and second information storage media; removing first frequencyrange components from an RF playback signal, obtained by irradiatingeach of the first and second information storage media with light anddetecting light reflected therefrom, and amplifying the amplitude ofsecond frequency range components thereof; and generating a sync clocksignal to do synchronization detection with respect to a digitalplayback signal that is obtained by digitizing the output of anequalizer. The first and second information storage media are rotated soas to achieve a first transfer rate and a second transfer rate at whichthe maximum playback frequency of the RF playback signal obtained fromthe first information storage medium is substantially equal to that ofthe RF playback signal obtained from the second information storagemedium.

In one preferred embodiment, supposing channel clock frequencies of thefirst and second information storage media are A and B, respectively,the second transfer rate is n (where 1≦n) times as high as a standardtransfer rate of the second information storage medium and the firsttransfer rate is n×(B/A) times as high as a standard transfer rate ofthe first information storage medium.

In another preferred embodiment, the first and second informationstorage media are rotated at a constant linear velocity.

In another preferred embodiment, the first and second informationstorage media are rotated at a constant angular velocity.

In another preferred embodiment, the first and second frequency rangesare substantially equalized with each other at the first and secondtransfer rates.

In another preferred embodiment, the same pair of setting constants isprovided for a voltage controlled oscillator and a frequency divider,which are used to generate the sync clock signal, either at the firsttransfer rate or at the second transfer rate.

In another preferred embodiment, a voltage controlled oscillator and afrequency divider are used to generate the sync clock signal and thefrequency divider has an integral frequency division ratio.

In another preferred embodiment, the optical disc drive also performs awrite operation on the first and second information storage media. Aftera read or write operation has been performed on the first or secondinformation storage medium for a predetermined period of time at aconstant linear velocity for a first location in the radial directionwhile the first or second information storage medium is being rotated ata first rotation velocity so as to achieve a transfer rate that ishigher than a standard read or write rate for the first or secondinformation storage medium, a write or read operation is performed onthe first or second information storage medium at the first rotationvelocity and at a constant angular velocity for a second location.

In one preferred embodiment, the second location is closer to the outeredge of the information storage medium than the first location is.

In another preferred embodiment, the second location is closer to theinner edge of the information storage medium than the first location is,and the transfer rate at the first location is at least 2.4 times ashigh as the standard transfer rate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing an optical disc drive according to afirst embodiment of the present invention.

FIG. 2 is a block diagram showing configurations for the equalizersection and register section shown in FIG. 1.

FIG. 3 is a block diagram showing configurations for the PLL section andregister section shown in FIG. 1.

FIG. 4 is a graph showing how the number of revolutions changes with theradial position of an optical pickup in a CLV method.

FIG. 5 is a graph showing transfer rate modes when the CLV method isadopted in this preferred embodiment.

FIG. 6 is a graph showing transfer rate modes when a CAV method isadopted in this preferred embodiment.

FIG. 7 is a graph showing relationships between the number ofrevolutions of the disc and the RF frequency band thereof for a CD and aDVD.

FIG. 8 is a schematic representation showing constants to be stored in asetting storage table according to this preferred embodiment.

FIG. 9 is a flowchart showing a procedure to load a CD according to thispreferred embodiment.

FIG. 10 is a flowchart showing a procedure to load a DVD according tothis preferred embodiment.

FIG. 11 is a block diagram showing an optical disc drive according to asecond embodiment of the present invention.

FIG. 12 is a block diagram showing configurations for the equalizersection and register section shown in FIG. 11.

FIG. 13 is a block diagram showing configurations for the VCO sectionand frequency divider shown in FIG. 12.

FIG. 14 shows exemplary oscillation frequency and frequency divisionratio for the VCO section and frequency divider of the conventionaloptical disc drive.

FIG. 15 shows exemplary oscillation frequency and frequency divisionratio for the VCO section and frequency divider shown in FIG. 13.

FIG. 16 is a block diagram showing an optical disc drive according to athird embodiment of the present invention.

FIG. 17 is a block diagram showing configurations for the equalizersection and register section shown in FIG. 16.

FIG. 18 schematically shows exemplary settings to be stored on a settingstorage table in a conventional optical disc drive.

FIG. 19 schematically illustrates the structure of an optical disc.

FIG. 20 schematically shows exemplary settings to be stored on a settingstorage table in an optical disc drive according to this preferredembodiment.

FIG. 21 is a block diagram showing an optical disc drive according to afourth embodiment of the present invention.

FIG. 22 shows a procedure to perform read and write operations accordingto this preferred embodiment.

FIG. 23 shows another procedure to perform read and write operationsaccording to this preferred embodiment.

FIG. 24 is a block diagram showing a conventional optical disc drive.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a block diagram showing an optical disc drive including anoptical disc controller according to a first preferred embodiment of thepresent invention. The optical disc drive 11 includes a disc motor 101,an optical pickup 103, an RF amplifier 104 and the optical disccontroller 114. The optical pickup 103 may include a laser diode 1021 toemit a laser beam to play a CD and another laser diode 1022 to emit alaser beam to play a DVD, for example.

In this optical disc drive 11, while the optical disc 102 is beingrotated by the disc motor 101 as a rotating mechanism, the opticalpickup 103 retrieves information from the optical disc 102 as an RFplayback signal. The RF playback signal is amplified by the RF amplifiercircuit 104. Then, the amplified RF playback signal is input to theoptical disc controller 114.

The optical disc controller 114 includes a system controller 111, asetting storage table 112, a disc type recognizing section 141, anequalizer section 105, a digitizing section 106, a demodulating section108, a PLL section 110 and a disc motor rotation control section 113. Inaddition, registers 109 and 110 are provided so as to make predeterminedsettings for the equalizer 105 and PLL section 107, respectively.

The RF playback signal is output from the RF amplifier to the disc typerecognizing section 141. In accordance with the signal intensitythereof, for example, the disc type recognizing section 141 determineswhether or not the type of the optical disc 102 loaded in this opticaldisc drive 11 and the selected laser diode 1021 or 1022 make anappropriate combination, and then passes the result to the systemcontroller 111.

The RF playback signal output from the RF amplifier is also input to theequalizer section 105 of the optical disc controller 114. The equalizersection 105 removes the RF noise, which is located outside of thepredetermined frequency band of the RF playback signal, and boosts thehigh frequency components of the RF playback signal, which havesignificantly deteriorated due to intersymbol interference, therebyoutputting an EQRF signal.

The EQRF signal is digitized by the digitizing section 106, and theresultant digital signal is input to the demodulating section 108 andPLL section 107. The PLL section 107 generates a sync clock signal,which is necessary for the demodulating section 108 to make a window forextracting data from the EQRF signal. In response to the sync clocksignal supplied from the PLL section 107, the demodulating section 108performs sync detection on the EQRF signal, thereby outputting digitizedread data. The errors of the read data are corrected by an errorcorrector circuit (not shown), thereby decoding it into validinformation.

FIG. 2 is a block diagram showing detailed configurations for theequalizer section 105 and the register 109. The equalizer section 105includes a bandpass filter 201 and a treble boost filter 202, while theregister 109 includes a cutoff frequency setting register 203 and adegree-of-boost setting register 204.

The RF playback signal obtained from the optical disc has been subjectedto an EFM modulation or 8-16 modulation, for example, and includesfrequency components to be determined by the optical disc with respectto one channel clock period T. For instance, a signal obtained from a CDincludes 3T to 11T frequency components, while one obtained from a DVDincludes 3T to 14T frequency components. The information stored on theCD or DVD is included as signals having these frequencies. Accordingly,to demodulate the information without errors, only effective frequencycomponents need to be extracted from the RF playback signal.

More specifically, the RF playback signal, detected by the opticalpickup 103, includes unnecessary frequency components (e.g., radiofrequency noise), and its signal amplitude changes from one frequencycomponent to another because of its deterioration due to intersymbolinterference, for example. Accordingly, to demodulate the informationcorrectly, those unnecessary frequency range components are removed fromthe RF playback signal by the bandpass filter 201 and the attenuatedfrequency range components are amplified by the treble boost filter 202,thereby equalizing the amplitudes of the respective frequencycomponents. The frequency at which the frequency band is limited (i.e.,the cutoff frequency) is set by the system controller 111 for the cutofffrequency setting register 203. The degree of amplification of theattenuated frequency components (i.e., the degree of boost) is also setby the system controller 111 for the degree-of-boost setting register204. As will be described in detail later, the constants to be suppliedto the cutoff frequency setting register 203 and degree-of-boost settingregister 204 are stored in the setting storage table 112.

FIG. 3 is a block diagram showing configurations for the PLL section 105and register 110. The PLL section 105 includes a phase detector 301, alow pass filter 302, a VCO 303 and a frequency divider 304. The register110 includes a VCO gain setting register 305 and a frequency divisionratio setting register 306. The digitized RF playback signal is input tothe phase detector 301, which detects a phase difference between thedigitized RF playback signal and the sync clock signal that is theoutput of the PLL section 107 (or frequency divider 304), therebyoutputting an error signal to the low pass filter 302. In response, thelow pass filter 302 outputs a control voltage, representing the phasedifference, to the VCO (voltage controlled oscillator) 303. The VCO 303oscillates a signal having a frequency associated with the controlvoltage and then supplies it to the frequency divider 304. And thefrequency divider 304 divides the frequency of the signal supplied fromthe VCO 303, thereby generating and outputting a sync clock signal.

The oscillation frequency of the VCO 303 and the frequency divisionratio of the frequency divider 304 are determined by the settingconstants to be defined by the VCO gain setting register 305 andfrequency division ratio setting register 306, respectively. The systemcontroller 111 chooses required setting constants from the settingstorage table 112 on which the constants to be set for the VCO gainsetting register 305 and frequency division ratio setting register 306are stored. The constants to be defined for the setting storage table112 will be described in detail later.

Next, the transfer rate modes of the optical disc drive 11 will bedescribed. The optical disc drive 11 can process a first informationstorage medium and a second information storage medium having mutuallydifferent storage densities. The storage density of the secondinformation storage medium is higher than that of the first informationstorage medium. Supposing channel clock frequencies of the first andsecond information storage media are A and B, respectively, the secondtransfer rate is n (where n is either a rational number or an irrationalnumber satisfying 1≦n) times as high as a standard transfer rate of thesecond information storage medium and the first transfer rate is n≦(B/A)times as high as a standard transfer rate of the first informationstorage medium. As used herein, the “transfer rate” refers to a rate atwhich information is read or written from/on a given optical disc.

In this case, the maximum playback frequency of the RF playback signalobtained from the first information storage medium at the first transferrate is substantially equal to that of the RF playback signal obtainedfrom the second information storage medium at the second transfer rate.A situation where “two maximum playback frequencies are substantiallyequal to each other” refers herein to a situation where the differencebetween the two maximum playback frequencies is within 10% of the lowermaximum playback frequency.

Thus, the setting to be defined for the PLL section 107 in playing thefirst information storage medium at the higher transfer rate can bematched with that for the second information storage medium.

Hereinafter, a specific example, in which the first and secondinformation storage media are a CD and a DVD, respectively, will bedescribed. First, it will be described how to play them by the CLV(constant linear velocity) method.

To be exact, the channel clock frequency of a CD is 4.3218 MHz and thechannel clock frequency of a DVD is 26.15625 MHz. In the followingdescription, however, calculations will be done with the channel clockfrequencies of a CD and a DVD rounded down to 4.32 MHz and 26.16 MHz,respectively. The channel clock frequency of a DVD is 6.06 times (i.e.,approximately 6 times) as high as that of a CD (i.e., 26.16/4.32).Accordingly, in playing a CD and a DVD by the CLV method, a standardtransfer rate (1×) is set as a transfer rate mode for a CD, and anotherstandard transfer rate (1×) is set as a transfer rate mode for a DVD.Also, a transfer rate approximately 6 times as high as the standardtransfer rate (6×) is defined as the higher transfer rate than thestandard transfer rate of the CD. Furthermore, if the transfer ratemodes of the DVD include a transfer rate that is twice as high as thestandard rate, an approximately 12 time higher transfer rate (12×) isdefined as another transfer rate mode for the CD. That is to say, thetransfer rate modes of the CD include 1×, 6× and 12×, while the transferrate modes of the DVD include 1× and 2×. The system controller 111instructs the disc motor rotation control section 113 to define thesetransfer rates.

In this case, the setting of the PLL section 107 to play a CD at the 6×transfer rate may be the same as that of the PLL section 107 to play aDVD at the standard transfer rate. In the same way, the setting of thePLL section to play a CD at the 12× transfer rate may be the same asthat of the PLL section 107 to play a DVD at the 2× transfer rate.Accordingly, the settings that are stored on the setting storage table112 and that are defined for the VCO setting register 305 and frequencydivision ratio setting register 306 to control the PLL section 107 needto be prepared in three sets for the CD standard transfer rate mode, DVDstandard transfer rate mode and DVD 2× transfer rate mode, respectively.

Such a control of the number of revolutions will be described in furtherdetail. In playing a single-layer DVD-ROM disc at the standard transferrate (1×), the playback operation is performed at a constant PLL clockfrequency of 26.16 MHz. Thus, the disc needs to be rotated such that thelinear velocity becomes equal to 3.49 m/s. More specifically, as shownin FIG. 4, the motor control section 113 of the disc motor 101 isinstructed to rotate the disc at 1,389 rpm when the optical pickup 103is located at an inside position (e.g., at a radial location of 24 mm)of the disc and at 575 rpm when the optical pickup 103 is located at anoutside position (e.g., at a radial location of 58 mm) of the disc.

In playing a two-layer DVD-ROM disc at the standard transfer rate (1×),the disc needs to be rotated at a linear velocity of 3.84 m/s to performthe playback operation at a constant PLL clock frequency of 26.16 MHz.More specifically, as shown in FIG. 4, the motor control section 113 ofthe disc motor 101 is instructed to rotate the disc at 1,529 rpm whenthe optical pickup 103 is located at an inside position (e.g., at aradial location of 24 mm) of the disc and at 633 rpm when the opticalpickup 103 is located at an outside position (e.g., at a radial locationof 58 mm) of the disc.

The linear velocity of a CD-ROM is lower than that of a DVD. In playinga CD-ROM disc at the standard transfer rate (1×), the disc needs to berotated at a linear velocity of 1.3 m/s to perform the playbackoperation at a constant PLL clock frequency of 4.321 MHz. Morespecifically, as shown in FIG. 4, the motor control section 113 of thedisc motor 101 is instructed to rotate the disc at 518 rpm when theoptical pickup 103 is located at an inside position (e.g., at a radiallocation of 24 mm) of the disc and at 214 rpm when the optical pickup103 is located at an outside position (e.g., at a radial location of 58mm) of the disc.

In playing a CD-ROM disc at the 6× transfer rate, as shown in FIG. 5,the motor control section 113 of the disc motor 101 is instructed torotate the disc at 3,105 rpm when the optical pickup 103 is located atan inside position (e.g., at a radial location of 24 mm) of the disc andat 1,285 rpm when the optical pickup 103 is located at an outsideposition (e.g., at a radial location of 58 mm) of the disc.

Also, if a mode to play a DVD-ROM disc at the 2× transfer rate isdefined, then a mode to play a CD-ROM disc at the 12× transfer rate canbe added without further increasing the PLL clock frequencies at the PLLsection 107. In that case, the motor control section 113 of the discmotor 101 is instructed to rotate the disc at 6,210 rpm when the opticalpickup 103 is located at an inside position (e.g., at a radial locationof 24 mm) of the disc and at 2,570 rpm when the optical pickup 103 islocated at an outside position (e.g., at a radial location of 58 mm) ofthe disc.

In this manner, by setting a transfer rate of the first informationstorage medium, which is higher than the standard transfer rate thereof,B/A times as high as a transfer rate of the second information storagemedium where A and B are the respective channel clock frequencies of thefirst and second information storage media, the processing loads can beeasily coped with to the very limits of the disc motor and othermechanisms of the optical disc drive and the performance limit of theoptical pickup thereof, for example.

Similar techniques are equally applicable to the read operations by theCAV (constant angular velocity) method. As shown in FIG. 6, when theoptical pickup 103 is located at an inside position (at a radiallocation of 24 mm) of the disc, a DVD disc is rotated at the standardtransfer rate of 1,389 rpm. If data is read from the vicinity of anoutside position of 58 mm of the disc being rotated at this rotationalvelocity, then the transfer rate will be 2.42 times (approximately 2.4times) as high as the standard transfer rate. In the CAV method, the PLLfrequency is intentionally equalized with that of the read data, therebyswitching the VCO oscillation frequencies between the inside and outsidepositions.

In that case, when the optical pickup 103 is located at an insideposition (at a radial location of 24 mm) of the disc, a CD disc isrotated at the 6× transfer rate of 1,389 rpm. If data is read from thevicinity of an outside position of 58 mm of the disc being rotated atthis rotational velocity, then the transfer rate will be 14.46 times(approximately 14.5 times) as high as the standard transfer rate.

If these two types of discs are rotated by the CAV method at therotational velocity described above, then the resultant transfer rateswill be equal to each other. Thus, the same frequency may be set for thePLL section.

It should be noted that the user data on a DVD starts from a radiallocation of approximately 24 mm while the user data on a CD starts froma radial location of approximately 25 mm. However, such a smalldifference is sufficiently negligible and should cause no seriousproblems in view of the variation in linearly velocity, for example.

Next, the setting of the equalizer section 105 will be described. Asdescribed above, by controlling the transfer rates, not just the settingof the PLL section 107 but also that of the equalizer section 105 forremoving noise from the RF playback signal and boosting the effectivesignal can be made common in multiple modes.

More specifically, the frequencies of an RF playback signal obtainedfrom a CD are defined to fall within the range of 3T to 11T (whereT=1/4.32 MHz) with respect to a reference channel clock frequency of4.32 MHz. Accordingly, at the standard transfer rate, the RF playbacksignal has a frequency range of 196 kHz to 720 kHz. On the other hand,the frequencies of an RF playback signal obtained from a DVD are definedto fall within the range of 3T to 14T (where T=1/26.16 MHz) with respectto a reference channel clock frequency of 26.16 MHz. Accordingly, at thestandard transfer rate, the RF playback signal has a frequency range of934 kHz to 4.36 MHz.

In playing a CD at the 6× transfer rate, the RF playback signal has afrequency range of 1.176 MHz to 4.320 MHz, which is roughly equal to thefrequency range of a DVD being played at the standard transfer rate.Accordingly, if the overlapping frequency ranges of the RF playbacksignals to be obtained by playing a CD at the 6× transfer rate and byplaying a DVD at the standard transfer rate are defined as a commonfrequency range, then the setting of the equalizer section 105 inplaying the CD at the 6× transfer rate may be equal to its setting inplaying the DVD at the standard transfer rate. That is to say, if thereis just one pair of settings to be supplied to the cutoff frequencysetting register 203 and degree-of-boost setting register 204, these twomodes can be coped with. The same statement is applicable to playing theCD and DVD at higher transfer rates. For example, the frequency range ofthe RF playback signal to be obtained by playing the CD at the 12×transfer rate substantially matches that of the RF playback signal to beobtained by playing the DVD at the 2× transfer rate.

FIG. 7 is a graph showing relationships between the number ofrevolutions of a CD or DVD and the RF playback signal frequency bandthereof. In FIG. 7, the range 701 represents an RF playback signalfrequency range defined for a CD with respect to the number ofrevolutions of the optical disc, while the range 702 represents an RFplayback signal frequency range defined for a DVD with respect to thenumber of revolutions of the optical disc.

For example, if a CD is rotated at a rotational velocity of 9,500 rpm asindicated by V_(CD) 703, then the frequency range of the RF playbacksignal to be detected from the optical disc will be from 18 MHz to 64MHz as indicated by the arrow 704. On the other hand, if a DVD isrotated at a rotational velocity of 2,000 rpm as indicated by V_(DVD)705, then the frequency range of the RF playback signal to be detectedfrom the optical disc will be from 18 MHz to 60 MHz as indicated by thearrow 706. Thus, their RF playback signal frequency ranges are almostequal to each other although the disc types and rotational velocitiesare different from each other.

This means that the equalizer section 105 and PLL section 107 to playthese two discs at the respective numbers of revolutions as indicated byV_(CD) 703 and V_(DVD) 705 may have equivalent characteristics. Morespecifically, this means that the four setting constants of the cutofffrequency setting register 203 and degree-of-boost setting register 204shown in FIG. 2 and the VCO oscillation frequency setting register 305and frequency division ratio setting register 306 shown in FIG. 3 areequal to each other between the CD and DVD. Accordingly, by setting thenumbers of revolutions of the CD and DVD equal to 9,500 rpm and 2,000rpm, respectively, the four register values that depend on the RFplayback signal frequency range can be used in common. FIG. 8schematically shows the setting storage table 112. In the situationdescribed above, just four constants need to be stored on the settingstorage table 112. If two sets of settings are needed for two types ofdiscs, then eight constants will have to be stored. Thus, compared withsuch a situation, the number of constants to be stored can be reducedsignificantly.

FIGS. 9 and 10 show a procedure to operate the optical disc drive 11with these numbers of revolutions adopted. Specifically, FIG. 9 shows aprocedure to play a CD, while FIG. 10 shows a procedure to play a DVD.

The frequency range of the RF playback signal obtained by playing a CDis equal to that of the RF playback signal obtained by playing a DVD.Thus, no matter whether the disc to play is a CD or a DVD, the cutofffrequency and degree of boost, which are needed as settings for theplayback equalizer section 105, are obtained from addresses Nos. 1 and 2of the setting storage table shown in FIG. 8 and respectively providedfor the cutoff frequency setting register 203 and degree-of-boostsetting register 204 shown in FIG. 2 (in Steps S14 and S20). In the sameway, the VCO gain and frequency division ratio, which are needed assettings for the PLL section 107, are obtained from addresses Nos. 3 and4 of the setting storage table 112 and respectively provided for the VCOgain setting register 305 and frequency division ratio setting register306 shown in FIG. 3 (in Steps S15 and S21). Thereafter, if the discloaded in the optical disc drive 11 is a CD, then the disc is rotated at9,500 rpm in Step 17. On the other hand, if the disc loaded is a DVD,then the disc is rotated at 2,000 rpm in Step 23.

As described above, according to this preferred embodiment, even inreading or writing data from/on multiple types of discs, there is noneed to provide two lines of signal processors such as equalizersections and PLL sections for the respective types of discs but theirprocessing is realized using the same circuits in common. In addition,the constants defined for the equalizer and PLL sections to be used incommon can also be common. Thus, the setting table to be provided in aROM or an EEPROM to store those constants can have a smaller capacity.As a result, the hardware scales of the optical disc controller andoptical disc drive can be reduced significantly.

Embodiment 2

FIG. 11 is a block diagram showing an optical disc drive including anoptical disc controller according to a second embodiment of the presentinvention. In the optical disc drive 12 shown in FIG. 11, any componentidentical with the counterpart of the optical disc drive 11 of the firstembodiment is identified by the same reference numeral. The optical discdrive 12 includes an optical disc controller 115 including a PLL section1101. FIG. 12 is a block diagram showing a configuration for the PLLsection 1101 shown in FIG. 11. In FIG. 12, any component having the sameor similar function as the counterpart of the PLL section 107 shown inFIG. 3 is identified by the same reference numeral. As shown in FIG. 12,the PLL section 1101 includes the phase detector 301, the low passfilter 302, a VCO 1201 and a frequency divider 1202.

FIG. 13 is a block diagram showing configurations for the VCO 1201 andfrequency divider 1202. The VCO 1201 includes a reference clockgenerator 1301 and at least two lines of oscillation frequency controlsections 1302. In accordance with the reference signal generated by thereference clock generator 1301 and a control voltage representing thephase difference supplied from the low pass filter 302, the oscillationfrequency control sections 1302 generate channel clock frequencies. Thechannel clock frequency varies with respect to the control voltage andone of the channel clock frequencies is selected by a VCO gain selector1303 based on the setting of the VCO gain setting register 305.

The reference clock frequency, oscillated by the VCO 1201, is thendivided by the frequency divider 1202. The frequency divider 1202includes at least two lines of frequency divider circuits 1305 withmutually different frequency division ratios. In accordance with thesetting of the frequency division ratio setting register 306, afrequency division ratio selector 1304 selects one of the frequencydivider circuits 1305 and the reference clock frequency is divided atthe frequency division ratio of the selected frequency divider circuit1305, thereby outputting the resultant channel clock pulse to thedemodulating section.

The sync clock signal to be output from the PLL section 1101 isgenerated by an appropriate combination of oscillation frequency controlsection 1302 in the VCO 1201 and frequency divider circuit 1305 in thefrequency divider 1202 so as to have the same frequency as the referenceclock frequency of the RF playback signal to be determined by thetransfer rate mode.

A conventional optical disc drive achieves multiple transfer rates,which are higher than the standard transfer rate an integral number oftimes (e.g., 16×, 8×, 4× and so on). Suppose a conventional optical discdrive includes a PLL section with a VCO 1401 that can oscillate areference clock frequency of 500 MHz and a frequency divider 1404 asshown in FIG. 14. For this conventional optical disc drive to play a DVDat 4× and 12× transfer rates, a frequency divider for generating a syncclock signal required in respective transfer rate modes from thereference clock signal needs to be prepared. The sync clock signalrequired at the 4× transfer rate may have a frequency of 108 MHz and thesync clock signal required at the 12× transfer rate may have a frequencyof 324 MHz, for example. The frequency division ratios of the frequencydivider circuits 1402 and 1403 required to generate these sync clocksignals are 1 to 4.63 for the 4× transfer rate and 1 to 1.54 for the 12×transfer rate, respectively. However, since these frequency divisionratios are not integral ones, the frequency divider circuits 1402 and1403 get complicated.

In contrast, in the optical disc drive 12 of this preferred embodiment,the oscillation frequency of the VCO and the frequency division ratio ofthe frequency divider are determined first, and a transfer rate to beachieved in the outermost area of the disc is selected according to thespecific combination of the oscillation frequency and frequency divisionratio selected, thereby determining the transfer rate (i.e., X timefaster playback operation). Then, the frequency division ratio canalways be an integral ratio and the configuration of the frequencydivider circuit can be simple enough.

FIG. 15 is a block diagram showing detailed configuration and settingsfor the frequency divider 1202 shown in FIG. 13. Suppose the VCO 1501has a reference clock frequency of 500 MHz and the frequency dividercircuits 1502 and 1503 have frequency division ratios of 1 to 8 and 1 to2, for example, to simplify the circuit configuration. The sync clocksignal that can be generated by this combination has a frequency of 62.5MHz for the frequency division ratio of 1 to 8 and a frequency of 250MHz for the frequency division ratio of 1 to 2, respectively. Thesesettings can be translated into 2.3 and 9.3, respectively, whenconverted into the multipliers of the DVD standard transfer rate. Thus,these non-integral numbers of 2.3 and 9.3 are adopted herein as the DVDtransfer rates, which form a part of the specifications of the opticaldisc drive 12.

However, even if these non-integral numbers are adopted as themultipliers of the transfer rate, the operation of the optical discdrive 12 will be hardly affected substantially. For example, comparedwith a conventional optical disc drive that can play a DVD at 2× and 9×transfer rates, no significant difference is recognized between theirperformances. This is because no matter whether the transfer rate is 2or 2.3 times as high as the standard transfer rate, each of thesetransfer rates is high enough to correct data errors to be producedwhile information is being retrieved from the DVD.

As described above, according to this preferred embodiment, even if anoptical disc drive should cope with multiple disc types and a pluralityof transfer rate modes, it is also possible to prevent its PLL section,including a VCO and a frequency divider, from increasing its circuitscale without affecting the performance of the drive substantially.

Embodiment 3

FIG. 16 is a block diagram showing an optical disc drive including anoptical disc controller according to a third embodiment of the presentinvention. In the optical disc drive 13 shown in FIG. 16, any componentidentical with the counterpart of the optical disc drive 11 of the firstembodiment is identified by the same reference numeral. FIG. 17 is ablock diagram showing a configuration for the PLL section 1603 of theoptical disc drive 13.

The optical disc drive 13 performs a read operation by rotating theoptical disc 102 by the CAV method. The optical disc drive 13 includes atraverse motor 1601, a traverse motor control section 1615 forcontrolling the traverse motor 1601, a location sensor 1604 and anoptical pickup position detector 1602. The optical pickup 103 is movedto an arbitrary radial location on the optical disc 102 by the traversemotor 1601, which functions as the moving mechanism, thereby readinginformation. In the CAV method, the transfer rate changes with aspecific read location on the optical disc 102. Accordingly, the syncclock frequency of the PLL section 1603 also needs to be changed withthe transfer rate.

For that purpose, the on-disc location specified by the optical pickup103 is detected by the location sensor 1604 and optical pickup positiondetector 1602. The result of this detection, i.e., information about theradial location of the optical pickup, is provided to the systemcontroller 111.

Alternatively, instead of providing the location sensor 1604 and opticalpickup position detector 1602, the address information recorded on theoptical disc 102 may be read so that the information about the positionof the optical pickup is drawn from the address information.

In a conventional CAV optical disc drive, disc read locations areclassified into a number of radial zones, and the VCO gain and frequencydivision ratio are sequentially switched whenever each of those zonesstarts to be read, thereby setting the sync clock frequency of the PLLsection into the best value on purpose. According to such a method, thesame number of setting constant sets as that of those zones need to beprepared for the PLL section. For example, if the optical disc isdivided into six radial zones, storage table areas of 12 bytes areneeded for a single transfer rate mode of a single optical disc as shownin FIG. 18. Accordingly, if the optical disc drive should cope withmultiple types of optical discs and a plurality of transfer rate modes,then the table areas for storing the setting constants to be given tothe PLL section will expand significantly.

Also, in the PLL section, the channel clock pulses are oscillated by theVCO so as to have its frequency defined, responsive to the referenceclock signal, within a frequency range that achieves the oscillationeven if the transfer rate has changed to a certain degree. Such afrequency range is called a “locking range (or locked frequency range)”.However, if the locking range were defined arbitrarily, then the VCOmight stop oscillating and the PLL might unlock and require re-lockingwhile the optical pickup is accessing a target location from an insideportion of the optical disc to an outside portion thereof, or viceversa. In that case, the access time will become much longer.

In the optical disc drive 13 of this preferred embodiment, the PLLsection 1603 is designed such that the ratio of the lower limit of thefrequency range of the channel clock pulses, which are oscillated by theVCO and of which the frequency is divided by the frequency divider, tothe upper limit thereof is equal to the ratio of the radius of abeginning of data location on the innermost area of the disc to that ofan end of data location on the outermost area thereof, and the settingsof the PLL section 1603 are unified over the entire area of the disc,thereby realizing a CAV read operation.

FIG. 19 schematically illustrates a single-layer DVD disc 1801. As shownin FIG. 19, information, including Leadin and Leadout, is stored on aninformation storage area 1803, which ranges from a radial location of 24mm to a radial location of 58 mm, on this DVD disc 1801. In retrievinginformation from this disc in a 5× transfer rate mode by the CAV method,the RF playback signal has a frequency range of 1.9 MHz to 9 MHz and therequired channel clock frequency is 54 MHz at the radial location of 24mm. On the other hand, at the radial location of 58 mm, the RF playbacksignal has a frequency range of 4.6 MHz to 21.6 MHz and the requiredchannel clock frequency is 130 MHz. The ratio of the outermost radius ofthe disc to the innermost radius thereof (i.e., 58/24) and the ratio ofthe channel clock frequencies (i.e., 130/54) are approximately equal toeach other and both about 2.4.

That is to say, by defining the locking range of the PLL section 1603from 50 MHz to 130 MHz and by equalizing the ratio of the upper limitfrequency to the lower limit frequency thereof with the ratio of theoutermost radius of the information storage area of the disc to theinnermost radius thereof (e.g., about 2.4 in this case), information canbe retrieved from the entire area of the disc with just a single set ofPLL settings. As a result, the circuit constants to be defined for thePLL section can also be reduced to 10 bytes for a single transfer ratemode of a single disc as shown in FIG. 20.

Thus, according to this preferred embodiment, just a single set ofconstants may be set for the PLL section in the CAV method, inparticular. Accordingly, the setting table in a ROM or an EEPROM can bedownsized and the overall hardware scale can be reduced significantly.Also, in accessing an arbitrary track in the radial direction, there isno need to make special settings for that access location. As a result,the access time can be shortened effectively.

Embodiment 4

FIG. 21 is a block diagram showing an optical disc drive including anoptical disc controller according to a fourth embodiment of the presentinvention. In the optical disc drive 14 shown in FIG. 21, any componentidentical with the counterpart of the optical disc drive 13 of the thirdembodiment is identified by the same reference numeral.

The optical disc drive 14 adopts CLV read and write methods to perform aread (playback) operation and a write (recording) operationsimultaneously (which is the so-called “simultaneous record and play”function) and to start a playback operation of a recorded program fromthe beginning even before the recording operation of the program isfinished (which is the so-called “chasing play back” function), amongother things.

The optical disc drive 14 includes a playback buffer memory 1613 fortemporarily storing the decoded data supplied from the demodulatingsection 108. The data once stored in the playback buffer memory 1613 issequentially transferred to the host computer 1614. The optical discdrive 14 further includes a write circuitry for writing data on theoptical disc 102. Specifically, the optical disc drive 14 includes arecording buffer memory 1612, a modulating section 1611 and an LD driversection 1610.

The write data, output from the host computer 1614, is temporarilystored in the buffer memory 1612. The modulating section 1611 receivesthe data that has been stored in the recording buffer memory 1612 andmodulates the data by a predetermined modulating method. Next, themodulated data is output to the laser diode driver section 1610, whichis provided to energize a writing light source (not shown) included inthe optical pickup 103. The laser diode driver section 1610 makes thewriting light source emit a light beam by supplying a drive signalthereto. By irradiating the storage layer of the optical disc 102 withthe light beam emitted, data can be written on the storage layer of theoptical disc 102.

The optical disc drive 14 of this preferred embodiment adopts the readand write techniques to be described below. In the followingillustrative example, the optical disc drive is supposed to perform awrite operation at an inside location on the optical disc and a readoperation at an outside location on the optical disc. Alternatively, theoptical disc drive may perform a read operation at an inside location onthe optical disc and a write operation at an outside location on theoptical disc.

As shown in FIG. 22, suppose information starts being written (e.g.,video information of a broadcast program starts being recorded) on afirst radial location 2201, which is defined by a radius of 25 mm, andat the same time, information (e.g., another video information) is readfrom another radial location 2203, which is located closer to the outeredge than the first location is and which is defined by a radius of 50mm. In that case, first, the optical pickup 103 is moved to the firstlocation 2201 with the radius of 25 mm and the optical disc is rotatedat 2,668 rpm, thereby starting the write operation. At this point intime, the transfer rate for the write operation is higher than thestandard write transfer rate and the data to be written has already beensufficiently stored in the recording buffer memory 1612.

At the first location (i.e., the location 2201 defined by the radius of25 mm), the write operation is carried out by the CLV method.Accordingly, as the write operation advances, the number of revolutionsof the optical disc 102 is decreased gradually as shown in FIG. 22.Since the transfer rate for the write operation is higher than thestandard write transfer rate, the amount of data stored in the recordingbuffer memory 1612 decreases. For example, when the amount of datastored in the recording buffer memory 1612 becomes either equal to zeroor less than a predetermined value at a location 2202 defined by aradius of 35 mm of the optical disc 102, the write operation may bestopped and the optical pickup 103 may be moved to the location definedby the radius of 50 mm. In this case, the system controller 111 does notinstruct the disc motor rotation control section 113 to change thenumber of revolutions of the disc. Thus, the information is read outfrom the location 2203, defined by the radius of 50 mm, with therotational velocity of 1,905 rpm for the location 2202 of the radius of35 mm maintained.

At the second location (i.e., the location 2203 defined by the radius of50 mm), the read operation is carried out by the CAV method. Consideringthe rotational velocity at this radial location, the transfer rate forthe read operation is higher than the standard CLV read transfer rate.Accordingly, the read transfer rate is higher than the transfer raterequired by the host computer 1614. As a result, data is sequentiallystored on the playback buffer memory. The data is continuously read fromthe location 2203 with the radius of 50 mm until the amount of read datastored in the playback buffer memory 1613 exceeds a predetermined value.In the meantime, the data to be written is sequentially stored in therecording buffer memory 1612.

When the data has been stored in the playback buffer memory 1613, theoptical pickup is moved back to the location 2202 with the radius of 35mm to write the data on the optical disc 102 again. In this case, sincethe number of revolutions of the disc motor remains 1,905 rpm, the writeoperation can be started again as soon as the optical pickup gets backto the location 2202 with the radius of 35 mm. The data that has beenstored while the read operation was performed is read out from therecording buffer memory 1612 and the write operation by the CLV methodis started again. In the meantime, the data that has been stored in theplayback buffer memory 1613 is transferred to the host computer 1614 andplayed back sequentially. The chasing play back or simultaneous recordand play operation is carried out by repeating this processing.

Most of various recordable or rewritable DVDs such as a DVD-RAM and aDVD-RW adopt the CLV technique in its read and write methods. Thus, fora conventional drive to perform the chasing play back or simultaneousrecord and play operation, the number of revolutions of the disc motorneeds to be switched. However, the motor ordinarily has a slow responsespeed. Also, as for a 12 cm DVD, the number of revolutions in the insideportion thereof is higher than that in the outside portion by as much as2.4 times. For that reason, it takes a long time to stabilize the numberof revolutions of the motor to a predetermined number after it has beenchanged once. Accordingly, to perform the chasing play back orsimultaneous record and play operation, the capacities of the buffermemories for temporarily storing the read and write data need to beincreased. Furthermore, since it is necessary to change the numbers ofrevolutions of the motor so often, the motor generates significant heator noise, thus deteriorating its reliability and usability (or quality).

According to this preferred embodiment, however, a read or writeoperation is performed by the CLV method at a first location and a writeor read operation is performed by the CAV method at a second location,which is closer to the outer edge than the first location is, with therotational velocity at the first location maintained. In performing theread or write operation by moving the optical pickup back and forthbetween the first and second locations, the rotational velocity of theoptical disc remains the same. Accordingly, there is no need to taketime to stabilize the rotational velocity of the motor. Thus, as soon asthe optical pickup reaches the first or second location, the read orwrite operation can be started immediately. As a result, the capacitiesof the recording and playback buffer memories can be decreased and thecost of the optical disc drive can be reduced. In addition, even inperforming the simultaneous record and play or chasing play backoperation, the quantity of heat generated by the motor can be minimizedand the optical disc drive can be operated quietly.

In the preferred embodiment described above, a read or write operationis performed by the CLV method at a first location and a write or readoperation is performed by the CAV method at a second location, which iscloser to the outer edge than the first location is, with the rotationalvelocity at the first location maintained. However, if the CLV read orwrite operation is performed at the first location at a transfer ratethat is at least 2.4 times as high as the standard transfer rate, thenthe second location can be closer to the inner edge than the firstlocation is.

For example, suppose a write operation by the CLV method is started at aradial location of 25 mm at 6,403 rpm resulting in a transfer rate thatis 2.4 times as high as the standard transfer rate as shown in FIG. 23.The write operation is performed by the CLV method. Accordingly, whenthe optical pickup reaches the first location 2205 with the radius of 35mm, the rotational velocity will be 4,572 rpm, which results in atransfer rate that is 2.4 times as high as the standard transfer rate atthat location.

Once the optical pickup has reached the first location 2205 with theradius of 35 mm, the optical pickup is moved back to the second location2204 with the radius of 25 mm, thereby reading the information stored.In this case, the rotational velocity of the motor is not changed butmaintained at 4,572 rpm and the read operation is performed by the CAVmethod (i.e., a combination of the radial location 2206 and the numberof revolutions as indicated by the dotted lines).

As shown in FIG. 23, the number of revolutions that results in the 2.4×transfer rate for the CLV method at the radial location 2204 with theradius of 25 mm is 6,403 rpm. However, even if the read operation isperformed at the number of revolutions of 4,572 rpm, a transfer ratethat is 1.7 times as high as the standard transfer rate can still beobtained. Accordingly, it is possible to avoid a situation where zerodata at the playback buffer discontinues the information being read.Such a procedure is particularly suitable to the chasing play backoperation for reading written data while performing a write operation.

The preferred embodiments described above may be effectively combinedwith each other. For example, by combining the first and secondpreferred embodiments, the optical disc drive 11 may be provided with afrequency divider with an integral frequency division ratio.Alternatively, by combining the first and third preferred embodiments,the optical disc drive 11 may be designed such that the frequency ratioof the locking range of the PLL section is equal to the ratio (2.4) ofthe outermost radius to the innermost radius of the information storagearea of the disc. As another alternative, by combining the first andfourth preferred embodiments, the disc motor and traverse motor may becontrolled such that the optical disc drive 11 can perform read andwrite operations by a combination of CLV and CAV methods to achieve thesimultaneous record and play or chasing play back function.

Furthermore, a combination of the second and third preferred embodimentsand any other combination may also be adopted effectively.

Although not illustrated specifically for the first through fourthpreferred embodiments, methods for controlling an optical disc driveaccording to the first through fourth preferred embodiments of thepresent invention described above may be carried out either by usinghardware components such as circuits made up of electronic parts or by amicrocomputer or the host computer of the optical disc drive. In thelatter case, a computer readable program (firmware) that is defined soas to carry out the procedure described above is stored in aninformation storage medium such as an EEPROM or a RAM.

INDUSTRIAL APPLICABILITY

An optical disc controller and an optical disc drive according to thepresent invention can perform a read or write operation on multipletypes of discs without providing two or more lines of signal processorssuch as equalizer sections or PLL sections for each disc but with commoncircuits. In addition, the constants to be defined for the equalizer andPLL sections can also be common, thus minimizing the setting table for aROM or an EEPROM and reducing the hardware scale significantly.

Also, even if the optical disc controller and optical disc drive of thepresent invention can cope with multiple types of discs or a pluralityof transfer rate modes, the circuit size of the PLL section thereof,including a VCO and a frequency divider, can still be reduced.

Furthermore, the optical disc controller and optical disc drive of thepresent invention need just one set of settings for the PLL section evenin the CAV playback mode, thus minimizing the setting table for a ROM oran EEPROM and reducing the hardware scale significantly.

Furthermore, the optical disc controller and optical disc drive of thepresent invention can reduce the capacities of recording and playbackbuffer memories in performing read and write operations simultaneouslyor in sequentially reading written data while continuing a writeoperation.

1. An optical disc controller for use in an optical disc drive thatplays optically a first information storage medium and a secondinformation storage medium having a higher storage density than that ofthe first information storage medium, the optical disc controllercomprising: a rotation control section for controlling a rotatingmechanism that rotates the first and second information storage media;an equalizer for removing first frequency range components from an RFplayback signal, obtained by irradiating each of the first and secondinformation storage media with light and detecting light reflectedtherefrom, and for amplifying the amplitude of second frequency rangecomponents thereof; and a phase locking section for generating a syncclock signal to do synchronization detection with respect to a digitalplayback signal that is obtained by digitizing the output of theequalizer, wherein the rotation control section rotates the first andsecond information storage media while controlling the rotatingmechanism such that RF playback signals are obtained at a first transferrate and at a second transfer rate, respectively, and wherein themaximum playback frequency of the RF playback signal obtained from thefirst information storage medium at the first transfer rate issubstantially equal to that of the RF playback signal obtained from thesecond information storage medium at the second transfer rate.
 2. Theoptical disc controller of claim 1, wherein supposing channel clockfrequencies of the first and second information storage media are A andB, respectively, the second transfer rate is n (where 1≦n) times as highas a standard transfer rate of the second information storage medium andthe first transfer rate is n×(B/A) times as high as a standard transferrate of the first information storage medium.
 3. The optical disccontroller of claim 1, wherein the rotation control section controls therotating mechanism such that the first and second information storagemedia rotate at a constant linear velocity.
 4. The optical disccontroller of claim 1, wherein the rotation control section controls therotating mechanism such that the first and second information storagemedia rotate at a constant angular velocity.
 5. The optical disccontroller of claim 1, wherein the equalizer is operated by beingprovided with a pair of setting constants that defines the first andsecond frequency ranges, respectively, and wherein the same pair ofsetting constants is applied to the first and second frequency rangeseither at the first transfer rate or at the second transfer rate.
 6. Theoptical disc controller of claim 1, wherein the phase locking sectionincludes a voltage controlled oscillator and a frequency divider, whichare operated at respective predetermined frequencies by being providedwith their setting constants, and wherein the same pair of settingconstants is provided for the voltage controlled oscillator and thefrequency divider either at the first transfer rate or at the secondtransfer rate.
 7. The optical disc controller of claim 1, wherein thephase locking section includes a frequency divider for dividing thefrequency by an integer.
 8. The optical disc controller of claim 1,wherein the optical disc drive also performs a write operation on thefirst and second information storage media, and wherein the optical disccontroller further includes a movement control section for driving amoving mechanism that moves an optical pickup in a radial direction ofthe first or second information storage medium, the optical pickup beingused to read or write a signal from/on the first and second informationstorage media, and wherein the movement control section and the rotationcontrol section control the moving mechanism and the rotating mechanism,respectively, such that after a read or write operation has beenperformed on the first or second information storage medium for apredetermined period of time at a constant linear velocity for a firstlocation in the radial direction while the first or second informationstorage medium is being rotated at a first rotation velocity so as toachieve a transfer rate that is higher than a standard read or writerate for the first or second information storage medium, a write or readoperation is performed on the first or second information storage mediumat the first rotation velocity and at a constant angular velocity for asecond location.
 9. The optical disc controller of claim 8, wherein thesecond location is closer to the outer edge of the information storagemedium than the first location is.
 10. The optical disc controller ofclaim 8, wherein the second location is closer to the inner edge of theinformation storage medium than the first location is, and wherein thetransfer rate at the first location is at least 2.4 times as high as thestandard transfer rate.
 11. An optical disc drive comprising: an opticalpickup for obtaining RF playback signals by irradiating a firstinformation storage medium and a second information storage medium,having a higher storage density than that of the first informationstorage medium, with light and detecting light reflected therefrom; arotating mechanism for rotating the first and second information storagemedia; and the optical disc controller of claim
 1. 12. An optical discdrive comprising: an optical pickup for writing a signal on a firstinformation storage medium and a second information storage medium,having a higher storage density than that of the first informationstorage medium, by irradiating the first and second information storagemedia with light and for obtaining RF playback signals by irradiatingthe first and second information storage media with light and detectinglight reflected therefrom; a rotating mechanism for rotating the firstand second information storage media; a moving mechanism for moving theoptical pickup in a radial direction of the first and second informationstorage media; and the optical disc controller of claim
 10. 13. A methodfor controlling an optical disc drive that plays optically a firstinformation storage medium and a second information storage mediumhaving a higher storage density than that of the first informationstorage medium, the method comprising the steps of: rotating the firstand second information storage media; removing first frequency rangecomponents from an RF playback signal, obtained by irradiating each ofthe first and second information storage media with light and detectinglight reflected therefrom, and amplifying the amplitude of secondfrequency range components thereof; and generating a sync clock signalto do synchronization detection with respect to a digital playbacksignal that is obtained by digitizing the output of an equalizer,wherein the first and second information storage media are rotated so asto achieve a first transfer rate and a second transfer rate at which themaximum playback frequency of the RF playback signal obtained from thefirst information storage medium is substantially equal to that of theRF playback signal obtained from the second information storage medium.14. The method of claim 13, wherein supposing channel clock frequenciesof the first and second information storage media are A and B,respectively, the second transfer rate is n (where 1≦n) times as high asa standard transfer rate of the second information storage medium andthe first transfer rate is n×(B/A) times as high as a standard transferrate of the first information storage medium.
 15. The method of claim13, wherein the first and second information storage media are rotatedat a constant linear velocity.
 16. The method of claim 13, wherein thefirst and second information storage media are rotated at a constantangular velocity.
 17. The method of claim 13, wherein the first andsecond frequency ranges are substantially equalized with each other atthe first and second transfer rates.
 18. The method of claim 13, whereinthe same pair of setting constants is provided for a voltage controlledoscillator and a frequency divider, which are used to generate the syncclock signal, either at the first transfer rate or at the secondtransfer rate.
 19. The method of claim 13, wherein a voltage controlledoscillator and a frequency divider are used to generate the sync clocksignal and the frequency divider has an integral frequency divisionratio.
 20. The method of claim 13, wherein the optical disc drive alsoperforms a write operation on the first and second information storagemedia, and wherein after a read or write operation has been performed onthe first or second information storage medium for a predeterminedperiod of time at a constant linear velocity for a first location in theradial direction while the first or second information storage medium isbeing rotated at a first rotation velocity so as to achieve a transferrate that is higher than a standard read or write rate for the first orsecond information storage medium, a write or read operation isperformed on the first or second information storage medium at the firstrotation velocity and at a constant angular velocity for a secondlocation.
 21. The method of claim 20, wherein the second location iscloser to the outer edge of the information storage medium than thefirst location is.
 22. The method of claim 20, wherein the secondlocation is closer to the inner edge of the information storage mediumthan the first location is, and wherein the transfer rate at the firstlocation is at least 2.4 times as high as the standard transfer rate.